Materials grinder

Abstract

A materials grinder has a materials receiving hopper, an exit opening into a shrouded grinding chamber and a powered ram for driving materials accumulated in the hopper to and through the exit into the grinding chamber. As grinding drum is rotatably disposed inside of a shroud adjacent the exit of the hopper to grind the ends of materials to be ground as they enter the grinding chamber and to continue to grinding as the materials are carried downwardly toward the bottom rear of the grinding chamber. The bottom of the shroud is open to receive an adjustable transverse shear bar assembly that is pivotally mounted to provide adjustment of the upper edges of the transverse shear bars with respect to the materials grinder drum.

I claim: 
     
       1. A materials grinder comprising: a hopper for receiving materials to be ground, said hopper including an open top, a horizontal floor and an exit opening adjacent said floor;   a ram in said hopper operable to displace materials on the floor of said hopper toward and through said exit opening;   a rotatable materials grinding drum adjacent said exit in said hopper, said drum having a surface including a plurality of abrading bits;   a concave adjacent said materials grinding drum mounted for rotation around an axis parallel to the axis of said grinding drum;   a cutter bar on said concave disposed below said exit opening and said drum in cooperating relationship with said abrading bits; and   a displaceable support engaging and urging said concave toward said grinding drum and being displaceable to allow said concave to pivot away from said grinding drum when ungrindable material is encountered to allow the ungrindable material to pass between said cutter bar and said grinding drum.   
     
     
       2. A materials grinder as defined in claim 1 further including a plurality of intermediate breaker bars on said concave. 
     
     
       3. A materials grinder as defined in claim 1 wherein said concave is urged toward said materials grinding drum by means of a hydraulic cylinder. 
     
     
       4. A materials grinder as defined in claim 3 wherein said hydraulic cylinder is coupled to an accumulator that functions to restore said hydraulic cylinder to an undisplaced condition after said hydraulic cylinder is displaced by ungrindable material passing between said cutter bar and said materials grinding drum. 
     
     
       5. A materials grinder as defined in claim 1 wherein the force exerted by said ram increases when the speed of rotation of said materials grinding drum increases and wherein the force exerted by said ram decreases when the speed of rotation of said materials grinding drum decreases so as substantially to avoid operating said materials grinding drum in either an overloaded or underloaded condition. 
     
     
       6. A materials grinder comprising: a hopper for receiving materials to be ground, said hopper including an open top, a horizontal floor and an exit opening adjacent said floor;   a ram in said hopper operable to displace materials on said floor of said hopper toward and through said exit opening;   a rotatable materials grinding drum adjacent said exit in said hopper, said drum having a surface including a plurality of abrading bits;   a concave adjacent said materials grinding drum mounted for rotation around an axis parallel to the axis of said grinding drum;   a cutter bar on said concave disposed below said exit opening and said drum in cooperating relationship with said abrading bits;   a hydraulic cylinder coupled to said concave so that pivoting movement of said concave displaces said hydraulic cylinder; and   an accumulator coupled to said hydraulic cylinder for returning said hydraulic cylinder to its undisplaced condition;   said hydraulic cylinder and said accumulator thereby functioning to hold said concave adjacent said grinding drum while grindable materials are being ground and to swing away from said grinding drum when ungrindable materials are encountered to allow said ungrindable materials to pass between said concave and said grinding drum.   
     
     
       7. A materials grinder as defined in claim 6 further including a plurality of intermediate breaker bars on said concave. 
     
     
       8. A materials grinder as defined in claim 6 wherein the force exerted by said ram increases when the speed of rotation of said materials grinding drum increases and wherein the force exerted by said ram decreases when the speed of rotation of said materials grinding drum decreases so as substantially to avoid operating said materials grinding drum in either an overloaded or underloaded condition. 
     
     
       9. A materials grinder comprising: a hopper for receiving materials to be ground, said hopper including an open top, a horizontal floor and an exit opening adjacent said floor;   a ram in said hopper operable to displace materials on said floor of said hopper toward and through said exit opening;   a rotatable materials grinding drum adjacent said exit in said hopper, said drum having a surface including a plurality of abrading bits;   a concave adjacent said materials grinding drum mounted for rotation around an axis parallel to the axis of said grinding drum;   a cutter bar on said concave disposed below said exit opening and said drum in cooperating relationship with said abrading bits;   a plurality of intermediate breaker bars on said concave;   a hydraulic cylinder coupled between said concave and a fixed anchor point so that pivoting movement of said concave away from said grinding drum compresses said hydraulic cylinder and so that extension of said hydraulic cylinder urges said concave toward said grinding drum;   an accumulator coupled to said hydraulic cylinder for receiving and accumulating hydraulic fluid discharged from said hydraulic cylinder when said hydraulic cylinder is compressed and for returning said hydraulic fluid to said hydraulic cylinder to extend said hydraulic cylinder when compressive forces on said hydraulic cylinder are released; and   a hydraulic control system coupled to said ram and responsive to the speed of rotation of said grinding drum for increasing the force exerted on said ram when the speed of rotation of said grinding drum increases and for reducing the force exerted on said ram when the speed of rotation of said grinding drum decreases.